1. Field of the Invention
The present invention relates to a composite drive system, for a compressor, capable of rotationally driving the compressor selectively or at the same time by either of two drive sources including a prime mover such as an internal combustion engine and a motor rotated by the power of a battery.
2. Description of the Related Art
To cope with the environmental problems in recent years, the practical application of an idle-stop (or xe2x80x9ceco-runxe2x80x9d) system has been promoted for stopping an internal combustion engine when a vehicle such as an automobile, with the engine mounted thereon, has stopped. When this system is used, as long as the vehicle is stationary, the compressor of the air-conditioning system of the particular vehicle also stops and the air-conditioning system is turned off, thereby causing the vehicle occupants to feel uncomfortable. In view of this, a xe2x80x9chybrid compressorxe2x80x9d is known which can be driven by either of two drive sources. Specifically, while the vehicle is stationary, the drive source is switched from the internal combustion engine to a motor rotationally driven by the power stored in a battery thereby to drive a compressor.
As a first well-known example of the hybrid compressor, a system capable of driving a swash-plate compressor selectively by one of two drive sources, including an internal combustion engine and a battery, has been proposed. In this system, a pulley having an electromagnetic clutch widely used for an automotive air-conditioning system is mounted on the drive shaft of a swash-plate compressor with the discharge amount thereof variable for each rotation. This pulley is adapted to be rotationally driven by the internal combustion engine through a belt. On the other hand, a motor driven by battery power is mounted on the drive shaft of the same compressor. In the normal operating mode of this system, the compressor is driven by the internal combustion engine, and when it is foreseen that the time has come to stop the engine or switch the drive source of the compressor from the engine to the motor, the angle of inclination of the swash plate of the compressor, changing with the magnitude of the cooling load, is detected. In the case where the inclination angle is large, indicating that the cooling load is heavy, the deenergization of the electromagnetic clutch and the stopping of the internal combustion engine are delayed. Thus, the compressor continues to be driven by the internal combustion engine. In the case where the cooling load is light and, therefore, the inclination angle of the swash plate is small, on the other hand, the electromagnetic clutch is immediately deenergized while at the same time stopping the internal combustion engine. Thus, the compressor is driven by the motor.
In a second well-known example of the hybrid compressor described in Japanese Unexamined Utility Model Publication No. 6-87678, as in the first well-known example, the drive shaft of the swash-plate compressor is rotationally driven selectively by two drive sources, i.e. by an internal combustion engine connected to the drive shaft of the swash-plate compressor through a belt, a pulley and an electromagnetic clutch, or by a motor driven by the battery directly and connected with the drive shaft of the compressor. The feature of this conventional hybrid compressor lies in that, while the compressor is driven by the internal combustion engine, the same motor is used as a generator from which power is acquired and stored in a battery.
The first well-known example of the hybrid compressor poses the problems that a swash-plate compressor of a variable displacement type having a complicated structure is used to make the discharge capacity variable, that the motor is only an auxiliary drive source for driving the compressor temporarily while the internal combustion engine is out of operation and is useless in other points, that a complicated control operation is required in spite of the rather poor functions and effects, and that the pulley for receiving the power from the internal combustion engine is very bulky because the electromagnetic clutch and the motor are built inside of the pulley.
On the other hand, the problems of the second well-known example of the hybrid compressor are that a swash-plate compressor of a variable displacement type having a complicated structure is used to make the discharge capacity variable, and that an electromagnetic clutch and a motor are built inside the pulley in radially superposed positions and therefore the pulley is bulkier than that of the first well-known example of the hybrid compressor. In the second well-known example, however, the motor is used also as a generator. Therefore, although this motor is not a simple auxiliary drive source used selectively in coordination with the internal combustion engine, the additional function of the motor for power generation is undesirably overlapped with the operation of the generator for charging the battery always attached to the internal combustion engine. Also, the motor for power generation is not used in other than the season when the cooling system is operated, and therefore the generator attached to the internal combustion engine cannot be eliminated and replaced by the motor. Thus, the use of the motor for driving the compressor as a generator leads to no special advantage. Both of the conventional hybrid compressors described above, therefore, have no greater advantage than the basic functions and effects of selectively using two drive sources at the sacrifice of a complicated compressor structure and the resulting considerably increased volume of the compressor and the related component parts.
An object of the present invention is obviate the above-mentioned problems of the prior art and to provide an improved compact, lightweight composite drive system for a compressor which can be fabricated at low cost and has such a novel configuration that the discharge capacity per unit time can be changed over a wide range even when using a fixed displacement compressor of a simple structure having a predetermined discharge capacity per rotation instead of a variable displacement compressor having a complicated structure with an electromagnetic clutch.
Another object of the invention is to provide an improved composite drive system for a compressor, in which an electromagnetic clutch is not required even in the case where a variable displacement compressor is used and in which the whole system including the compressor and the input means receiving power from the prime mover and the motor for driving the compressor has a smaller size and weight than the conventional hybrid compressor.
According to one aspect of the invention, there is provided a composite drive system for a compressor which obviates the aforementioned various problems of the prior art in the manner described below (claim 1).
The composite drive system according to this aspect of the invention uses a dynamo-electric machine (hereinafter referred to as xe2x80x9cthe dynamotorxe2x80x9d) capable of operating both as a motor and as a generator and including a rotatable field portion and a rotatable armature portion, wherein a selected one of the armature portion and the field portion of the dynamotor is operatively interlocked with the output shaft of the prime mover, while the other one of the armature portion and the field portion is operatively interlocked with the drive shaft of the compressor. The dynamotor is connected with a power supply unit such as a battery through a power control unit.
In the case where the dynamotor is operated in motor mode by the power control unit, the turning effort of the output shaft of the prime mover received by selected one of the armature portion and the field portion of the dynamotor is output from the other one of the armature portion and the field portion as a turning effort having a higher rotational speed by adding the rotational speed generated between the armature portion and the field portion, as a motor, to the rotational speed received, so that the drive shaft of the compressor is driven by the particular turning effort. As a result, the discharge capacity per unit time of even a compact, lightweight compressor of fixed displacement type having a small discharge capacity per rotation can be freely controlled either upward or downward. In addition, when the prime mover is stationary, the compressor can be driven only by the dynamotor and the power supply unit, and in the case where the dynamotor is set in unloaded operation mode by disconnecting the dynamotor and the power supply unit, by the power control unit, the compressor can be stopped without using the electromagnetic clutch while the prime mover is in operation.
Further, in the event that the output rotational speed of the prime mover is excessively increased, the dynamotor is operated in generator mode by the power control unit, and by thus recovering the generated power to the power supply unit, the turning effort of the output shaft of the prime mover received from a selected one of the armature portion and the field portion of the dynamotor is partially converted into power and stored in the power supply unit. As a result, a reduced rotational speed is output from the other one of the armature portion and the field portion by adding the negative rotational speed generated between the armature portion and the field portion as a generator to the rotational speed received, so that the drive shaft of the compressor is driven by the motive power with an arbitrarily reduced rotational speed.
In this way, the wasteful consumption of energy is eliminated on the one hand and, even in the case where the rotational speed of the prime mover is excessively increased for the compressor of fixed displacement type, the discharge capacity per unit time of an arbitrary magnitude required of the compressor can be secured by freely controlling the rotational speed of the compressor on the other hand. Also, in the case where the power supply unit has no margin for receiving the power from the dynamotor, the rotational speed of the compressor can be regulated at the desired level, for example, by performing the duty factor control operation for switching between the unloaded operation mode and the generator mode at short time intervals.
According to another aspect of the invention, there is provided a composite drive system for a compressor which obviates the aforementioned various problems of the prior art in the manner described below (claim 6).
The composite drive system according to this aspect of the invention comprises a dynamotor capable of operating both as a motor and as a generator, and including a rotor having a plurality of permanent magnets on the peripheral surface thereof and an iron core having a plurality of coils and fixed at a position in opposed relation to the rotor. The dynamotor is connected to a power supply unit like a battery through a power control unit. A one-way clutch can be interposed between the rotor of the dynamotor and the input means receiving power from a prime mover constituting a main drive source.
In this dynamotor, the rotor is kept rotated as long as the prime mover constituting the main drive source such as an internal combustion engine is in operation. Therefore, the dynamotor is kept in generator mode and can always generate power as a generator, except when it is used in motor mode for driving the compressor in place of the main prime mover. This power is stored in the power supply unit through the power control unit. Even in the season when the compressor is not operated, therefore, the dynamotor operates as a generator.
A specific embodiment of the invention is the internal combustion engine mounted on a vehicle as a preferred prime mover. The compressor can be suitably used as a refrigerant compressor of an air-conditioning system of a vehicle. The battery mounted on the vehicle can be used as a power supply unit. In such a case, even when the internal combustion engine is stationary under idle-stop control, the air-conditioning system can be operated by driving the compressor using the dynamotor and the battery.
The use of the dynamotor of magnet type having at least a permanent magnet simplifies the structure, and therefore makes it possible to manufacture a compact, lightweight dynamotor at a lower cost. This is also true in the case where the dynamotor is incorporated in a driven pulley on the side of the compressor rotationally driven through a belt by the output shaft of a prime mover such as an internal combustion engine. In any case, the whole configuration of the composite drive system for the compressor can be reduced in size and weight, and can be easily built in a limited space such as the engine compartment of a vehicle.